Filament spool roller for Ender

During repetitive retractions and deretractions, a full/heavy spool can start rocking back and forth causing strain on the extruder gear and lead to filament grinding and/or artifacts in the print. I've tried a few different filament holder designs with ball bearings and either had the spool unwind while printing causing tangles or they needed table space to set the spool on. I came up with this design that utilizes the stock spool holder to keep everything attached to the printer while allowing the spool to easily spin but only while extruding material.

With the spool position on the side of the printer, my bearing roller is positioned at about 10 o'clock. This allows the spool to rest against the original spool holder at about the 2 o'clock position which eliminates a free running spool and the rocking motion of the spool during retractions. I gentle pull on the filament from the extruder transfers most of the weight of the spool onto the bearing roller allowing it to smoothly